Effects of the 4th dose of Covid-19 vaccine

At the end of March, the US Food and Drug Administration approved a second booster dose of Covid-19 vaccine for vulnerable populations. Those who are 50 years of age or older, some of whom are immunocompromised, are more susceptible to severe illness, hospitalization and death. The interval between the 3rd and 4th shots is 4 months.

In Israel, a high-risk population gets a 4th dose in January. Recently, the UK started giving a 4th dose to people aged 75 and over. In Germany, people over 60 are eligible for the 4th shot.

Efficacy of the 3rd dose

There is strong evidence that a 3rd dose of Covid-19 vaccine is important to ensure robust immunity against the Omicron variant for all age groups. This is partly because the effectiveness of the first two shots declines over time and Omicron is somewhat able to evade immunity from the vaccine and has been infected.

The UK Health Security Agency currently has follow-up data for 15 weeks after the 3rd dose. Accordingly, the vaccine’s effectiveness in preventing hospitalization is much better than against infection but is also decreasing with time. time.

A recent study evaluated the persistence of a 3rd dose of Moderna tapering off over 6 months.

The above analyzes aggregated all age groups. In addition, older adults do not have as long-lasting immune responses as younger populations. As a result, the incidence of Covid-19 is much higher in people 65 years of age and older.

Data on 4th dose

Now that many Israelis have had the 4th dose for several months, scientists have some data to assess the effectiveness.

In the study, published in the New England Journal of Medicine, the authors assessed the rate of Covid-19 infection and worsening after the fourth dose of 1 million people 60 years of age and older in Israel. Accordingly, the rate of Covid-19 infection in this group is half that of those who have just received the 3rd dose. Hospitalization rates of both groups are low.

Another analysis evaluated the effect of a fourth dose on young Israeli healthcare workers. The results confirmed that antibody levels decreased significantly 5 months after the 3rd dose. But the effect of the 4th dose was not different from the 3rd dose. In other words, the 4th dose may not provide benefit. for a young, healthy population.

For people who have been infected with Omicron, the combination of immunity from the vaccine and Covid-19 is called “hybrid immunity”. More than 30 studies have shown that hybrid immunity offers broader possibilities.

Therefore, it is not reasonable to skip the 4th injection despite being infected with Omicron. This doesn’t mean everyone has to try to get Covid-19.

An Yen (According to Conversation)